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  Java SE基础之面向对象(一)
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      <h2 id="一、类"><a href="#一、类" class="headerlink" title="一、类"></a>一、类</h2><h4 id="什么是类"><a href="#什么是类" class="headerlink" title="什么是类"></a>什么是类</h4><p>类是对现实生活中一类具有个体属性和行为的事物的抽象，确定对象将会有的属性和行为</p>
<h4 id="类的组成"><a href="#类的组成" class="headerlink" title="类的组成"></a>类的组成</h4><ul>
<li><strong>属性</strong>：在类中通过<strong>成员变量</strong>来体现（类中方法外的变量）</li>
<li><strong>行为</strong>: 在类中通过<strong>成员方法</strong>体现（去掉static关键字）</li>
</ul>
<h4 id="类的定义"><a href="#类的定义" class="headerlink" title="类的定义"></a>类的定义</h4><p>步骤：</p>
<p>①<em>定义类</em></p>
<p>②<em>编写类的成员变量</em></p>
<p>③<em>编写类的成员方法</em></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> 类名</span>&#123;</span><br><span class="line">    <span class="comment">//成员变量</span></span><br><span class="line">    数据类型 变量<span class="number">1</span>;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">//成员方法</span></span><br><span class="line">    方法<span class="number">1</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<a id="more"></a>
<h2 id="二、对象"><a href="#二、对象" class="headerlink" title="二、对象"></a>二、对象</h2><h4 id="对象的理解"><a href="#对象的理解" class="headerlink" title="对象的理解"></a>对象的理解</h4><p>对象是类的一个实例，现实生活中，万物皆可对象化，如车、狗等，它们都有自己的状态（颜色、种类等）和行为（跑）</p>
<p>在方法中我们可以将对象实例化后访问对象内的属性，调用对象的方法来操作对象。</p>
<h4 id="对象的使用"><a href="#对象的使用" class="headerlink" title="对象的使用"></a>对象的使用</h4><h5 id="创建对象"><a href="#创建对象" class="headerlink" title="创建对象"></a>创建对象</h5><ul>
<li>格式：类名 对象名=new 类名();</li>
<li>范例：Person p=new Person();</li>
</ul>
<h5 id="使用对象"><a href="#使用对象" class="headerlink" title="使用对象"></a>使用对象</h5><p>1、<strong>使用成员变量</strong></p>
<ul>
<li>格式： 对象名 变量名</li>
<li>范例： p.height</li>
</ul>
<p>2、<strong>使用成员方法</strong></p>
<ul>
<li>格式：对象名.方法名()</li>
<li>范例： p.call()</li>
</ul>
<h2 id="三、对象执行内存图解"><a href="#三、对象执行内存图解" class="headerlink" title="三、对象执行内存图解"></a>三、对象执行内存图解</h2>
<div style="position:relative;width:100%;height:0;padding-bottom:75%;">
<iframe src="//player.bilibili.com/player.html?aid=61869077&bvid=BV1wt411u7KE&cid=107828417&page=103" scrolling="no" border="0" frameborder="no" framespacing="0" allowfullscreen="true" style="position: absolute;width:100%;height: 100%;left: 0;top: 0;"> </iframe>
</div>



<p>多个对象指向相同地址</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">StudentTest</span></span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span></span>&#123;</span><br><span class="line">        Student s1=<span class="keyword">new</span> Student();</span><br><span class="line">        s1.name=<span class="string">"张三"</span>;</span><br><span class="line">        System.out.println(s1.name);</span><br><span class="line">        Student s2=s1;</span><br><span class="line">        s2.name=<span class="string">"李四"</span>;</span><br><span class="line">        System.out.println(s1.name);</span><br><span class="line">        System.out.println(s2.name);        </span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p><strong>执行流程</strong>：</p>
<ul>
<li>首先main方法被加载到栈内存</li>
<li>创建第一个对象，Student s1出现在栈内存，new Student()出现在堆内存</li>
<li>堆内存会产生一个空间地址，并将地址赋给s1</li>
<li>修改对象s1的name属性，输出</li>
<li>将第一个对象地址赋给第二个对象s2,此时两个对象的指向相同</li>
<li>赋值，输出</li>
</ul>
<p>输出结果：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">张三</span><br><span class="line">李四</span><br><span class="line">李四</span><br></pre></td></tr></table></figure>

<h2 id="四、成员变量与局部变量的区别"><a href="#四、成员变量与局部变量的区别" class="headerlink" title="四、成员变量与局部变量的区别"></a>四、成员变量与局部变量的区别</h2><table>
<thead>
<tr>
<th>区别</th>
<th>成员变量</th>
<th>局部变量</th>
</tr>
</thead>
<tbody><tr>
<td>类中位置不同</td>
<td>类中方法外</td>
<td>方法内或者方法声明上</td>
</tr>
<tr>
<td>内存中位置不同</td>
<td>堆内存</td>
<td>栈内存</td>
</tr>
<tr>
<td>生命周期不同</td>
<td>随着对象的存在而存在，消失而消失</td>
<td>随着方法的调用而存在，调用完毕而消失</td>
</tr>
<tr>
<td>初始化值不同</td>
<td>有默认的初始化值</td>
<td>没有默认的初始化值，必须先定义，赋值，才能使用</td>
</tr>
</tbody></table>
<h2 id="五、private关键字"><a href="#五、private关键字" class="headerlink" title="五、private关键字"></a>五、private关键字</h2><ul>
<li>是一个权限修饰符</li>
<li>可以修饰成员（成员变量和成员方法）</li>
<li>作用是保护成员不被别的类使用，被private修饰的成员只在本类中才能访问。</li>
</ul>
<p>针对private修饰的成员变量，如果需要别其他类使用，需提供相应操作：</p>
<ul>
<li>提供<strong>get变量名()</strong>方法，用于获取成员变量的值，方法用public修饰</li>
<li>提供<strong>set变量名(参数)</strong>方法，用于设置成员变量的值，方法用public修饰</li>
</ul>
<p>练习：<br>编写一个标准类，要求：成员变量用private修饰，提供对应的<em>get()</em>/<em>set()</em>方法</p>
<p><a href="">Student.java</a></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> Student;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Student</span> </span>&#123;</span><br><span class="line">   <span class="keyword">private</span> String name;</span><br><span class="line">   <span class="keyword">private</span> <span class="keyword">int</span> age;</span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String n)</span></span>&#123;</span><br><span class="line">	   name=n;</span><br><span class="line">   &#125;</span><br><span class="line">   <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span></span>&#123;</span><br><span class="line">	   <span class="keyword">return</span> name;</span><br><span class="line">   &#125;</span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setAge</span><span class="params">(<span class="keyword">int</span> a)</span></span>&#123;</span><br><span class="line">	   age=a;</span><br><span class="line">   &#125;</span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getAge</span><span class="params">()</span></span>&#123;</span><br><span class="line">	   <span class="keyword">return</span> age;</span><br><span class="line">   &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p><a href="">StudentDemo.java</a></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> Student;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">StudentDemo</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">	<span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>&#123;</span><br><span class="line">		Student s=<span class="keyword">new</span> Student();</span><br><span class="line">		s.setName(<span class="string">"张三"</span>);</span><br><span class="line">		s.setAge(<span class="number">23</span>);</span><br><span class="line">		System.out.println(s.getName()+<span class="string">","</span>+s.getAge());</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
      
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        <!-- Default (PhotoSwipeUI_Default) interface on top of sliding area. Can be changed. -->
        <div class="pswp__ui pswp__ui--hidden">

            <div class="pswp__top-bar">

                <!--  Controls are self-explanatory. Order can be changed. -->

                <div class="pswp__counter"></div>

                <button class="pswp__button pswp__button--close" title="Close (Esc)"></button>

                <button class="pswp__button pswp__button--share" style="display:none" title="Share"></button>

                <button class="pswp__button pswp__button--fs" title="Toggle fullscreen"></button>

                <button class="pswp__button pswp__button--zoom" title="Zoom in/out"></button>

                <!-- Preloader demo http://codepen.io/dimsemenov/pen/yyBWoR -->
                <!-- element will get class pswp__preloader--active when preloader is running -->
                <div class="pswp__preloader">
                    <div class="pswp__preloader__icn">
                        <div class="pswp__preloader__cut">
                            <div class="pswp__preloader__donut"></div>
                        </div>
                    </div>
                </div>
            </div>

            <div class="pswp__share-modal pswp__share-modal--hidden pswp__single-tap">
                <div class="pswp__share-tooltip"></div>
            </div>

            <button class="pswp__button pswp__button--arrow--left" title="Previous (arrow left)">
            </button>

            <button class="pswp__button pswp__button--arrow--right" title="Next (arrow right)">
            </button>

            <div class="pswp__caption">
                <div class="pswp__caption__center"></div>
            </div>

        </div>

    </div>

</div>

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/photoswipe@4.1.3/dist/photoswipe.min.css">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/photoswipe@4.1.3/dist/default-skin/default-skin.css">
<script src="https://cdn.jsdelivr.net/npm/photoswipe@4.1.3/dist/photoswipe.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/photoswipe@4.1.3/dist/photoswipe-ui-default.min.js"></script>

<script>
    function viewer_init() {
        let pswpElement = document.querySelectorAll('.pswp')[0];
        let $imgArr = document.querySelectorAll(('.article-entry img:not(.reward-img)'))

        $imgArr.forEach(($em, i) => {
            $em.onclick = () => {
                // slider展开状态
                // todo: 这样不好，后面改成状态
                if (document.querySelector('.left-col.show')) return
                let items = []
                $imgArr.forEach(($em2, i2) => {
                    let img = $em2.getAttribute('data-idx', i2)
                    let src = $em2.getAttribute('data-target') || $em2.getAttribute('src')
                    let title = $em2.getAttribute('alt')
                    // 获得原图尺寸
                    const image = new Image()
                    image.src = src
                    items.push({
                        src: src,
                        w: image.width || $em2.width,
                        h: image.height || $em2.height,
                        title: title
                    })
                })
                var gallery = new PhotoSwipe(pswpElement, PhotoSwipeUI_Default, items, {
                    index: parseInt(i)
                });
                gallery.init()
            }
        })
    }
    viewer_init()
</script>



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